MOG is a type of glycoprotein on oligodendrocyte which is only found in central nervous system.[11] And impairment of the blood brain barrier (BBB) may play an important role in pathogenesis of MOG-EM.[12–14] The tumor itself might represent the immune response and immune monitoring abnormalities in human beings.[6] In our case report, the impairment of BBB and oligodendrocyte might consist of four factors, including the impairment of tumor, tumor resection, postoperative radiation treatment and chemotherapy. Here, ART4 is linked to erythema multiforme.